Vacuum assisted walking beam apparatus

ABSTRACT

A vacuum assisted multiple position walking beam apparatus ( 10 ), which has products ( 20 ) placed thereon.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a vacuum assisted multiple position walkingbeam apparatus, which precisely advances and locates products, which areplaced and advanced thereon in a row for straight line productionoperations.

2. Description of the Prior Art

In the Photovoltaic industry silicone wafers or cells are assembled intopanels by arranging them in an x-y matrix. This process has beenaccomplished manually and through the use of automation. The automationconcepts can be summarized into two basic methods. The first method iscommonly referred to as matrixing, and involves placing each cell into agrid fixture one at a time, and then moving the grid around to soldereach cell together. The second approach is commonly referred to asstringing, and involves placing and soldering each cell into a row ofthe matrix individually, thereby forming “strings” of cells. Thesestrings can then be placed into storage buffers or placed directly ontoa glass to form the panel. The stringing method represents a morecompact solution which ultimately requires less floor space, and isgaining popularity in the industry. The automation that is currentlyavailable for stringing solar cells utilizes a metal belt to transportthe string as it is being constructed. Many problems exist with themetal belt apparatus, which include belt tracking, belt warpage, beltlife, difficulty in precisely holding and supporting the wafers as theyare transported and soldered, and the expense involved in maintainingand operating the equipment.

The multiple position vacuum assisted walking beam apparatus of theinvention is useful in the photovoltaic industry and any industry inwhich wafer like products must be precisely located and advanced in astraight line for processing, which apparatus provides precisionlocation, advancement and holding of the products for processing withoutthe problems of previously available equipment.

SUMMARY OF THE INVENTION

In developing apparatus for assembling strings of photovoltaic cellsseveral criteria were involved. The apparatus must maintain thealignment of the cells as they are placed next to each other, must nottouch or damage the cell edges, and must be easily configured fordifferent cell sizes and string lengths. Because the cell edges arefragile, a concept was required that would not involve touching the celledges to move the cell or string. Vacuum was selected as the best methodto grip or hold the cell after it was placed into the string. Thewalking beam concept was selected for transporting and processing thestrings, which included a movable center beam, and two stationary sidebeams. With a conventional walking beam mechanism, two separate beamsare utilized. One beam remains stationary while the other beam moves upand down in the vertical axis and back and forth in the horizontal axis.The moving beam will lift the string from the stationary beam, carry thestring forward, lower the string onto the stationary beam, move belowthe level of the string, and retract to the home position. In order tohold the cells, vacuum was added to both the moving beam, and thestationary beams. Vacuum switching was provided to operate when themoving beam was exactly coplanar with the stationary beams, so the cellwas not pulled by the vacuum and broken. To solve this problem, a thirdposition was introduced to the center beam. The moving center beamtherefor has three vertical positions described as; above the stationarybeams, coplanar with the stationary beams, and below the stationarybeams. Vacuum is directed into the moving beam when the string is beinglifted, carried forward, and lowered to the coplanar position. When themoving center beam is coplanar with the stationary beams vacuum isswitched from the moving beam to the stationary beams and thestring/cells is/are then anchored to the stationary beams. The movingbeam, now without vacuum, is free to drop below the string and retractin preparation for the next move. At this time, the next cell is placedon the stationary beams and soldered to the adjacent cell. The string isalways held by vacuum whether it is held to the stationary beams or heldto the moving beam. At no time is the string without vacuum. This isimportant as the aesthetics and performance of the solar module are duein part to the alignment and positioning of the cells within the module.

It has now been found that a multiple position vacuum assisted walkingbeam apparatus can be constructed, which has wafer like products placedthereon, which apparatus includes a movable center beam and fixed sidebeams, one on each side of the center, with vacuum selectively appliedto the center beam and the side beams to support the products as theyare transported and processed.

The principal object of the invention is to provide a vacuum assistedmultiple position walking beam apparatus for support, attachment, andtransport of products in a string configuration.

A further object of the invention is to provide apparatus of thecharacter aforesaid which is precise and positive in operation.

A further object of the invention is to provide apparatus of thecharacter aforesaid which is of rigid construction.

A further object of the invention is to provide apparatus of thecharacter aforesaid which is resistant to wear and fatigue.

A further object of the invention is to provide apparatus of thecharacter aforesaid, which is useful with a wide variety of products andmanufacturing operations.

A further object of the invention is to provide apparatus of thecharacter aforesaid, which is simple to construct but rugged and longlasting in service.

Other objects and advantageous features of the invention will beapparent from the description and claims.

DESCRIPTION OF THE DRAWINGS

The nature and characteristic features of the invention will be morereadily understood from the following description taken in connectionwith the accompanying drawings forming part hereof in which;

FIG. 1 is a side elevational view of a multiple position vacuum assistedwalking beam apparatus, in initial position with a single wafer thereon;

FIG. 2 is an end view of the apparatus of FIG. 1;

FIG. 3 is a view similar to FIG. 1 with the center beam of the apparatusin raised position;

FIG. 4 is an end view of the apparatus of FIG. 3;

FIG. 5 is a view similar to FIG. 3, illustrating the center beam in theforward or advanced position;

FIG. 6 is an end view of the apparatus of FIG. 5;

FIG. 7 is a view similar to FIG. 1, with the center beam in neutralposition, at the same level as the side beams;

FIG. 8 is an end view of the apparatus of FIG. 7;

FIG. 9 is a view similar to FIG. 7, with the center beam lowered belowthe side beams;

FIG. 10 is an end view of the apparatus of FIG. 9;

FIG. 11 is a view similar to FIG. 9, with the center beam in retractingcondition;

FIG. 12 is an end view of the apparatus of FIG. 11;

FIG. 13 is a view similar to FIG. 1, with the center beam in initialposition;

FIG. 14 is an end view of the apparatus of FIG. 13;

FIG. 15 is a view similar to FIG. 1 with a string of wafers thereon,with the center beam in the forward position, and

FIG. 16 is a top plan view, enlarged, of the apparatus of the invention.

It should, of course, be understood that the description and drawingsherein are merely illustrative and that various modifications andchanges can be made in the structures disclosed without departing fromthe spirit of the invention.

Like numbers refer to like parts throughout the several views.

DESCRIPTION OF THE PREFERRED EMBODIMENT

When referring to the preferred embodiment, certain terminology will beutilized for the sake of clarity. Use of such terminology is intended toencompass not only the described embodiment, but also technicalequivalents which operate and function in substantially the same way tobring about the same result.

Referring now more particularly to FIGS. 1-14 inclusive, the walkingbeam apparatus 10 of the invention is therein illustrated. The apparatus10 includes a pair of elongated side beams 11 and 12, which arestationary and fixed to a frame (not shown) of a machine (not shown)with which they are used. The beams 11 and 12 are spaced apart and acenter beam 14 is provided between the stationary beams 11 and 12.

The center beam 14 is movable between the stationary beams, vertically,and horizontally to be described.

The center beam 14 is mounted to well known mechanism (not shown) whichprovides its movement. The stationary beams 11 and 12, and the centerbeam 14 are preferably of metal with a plurality of spaced vacuum holes15 therein, which are connected to a selectively controlled vacuumsource (not shown) of well known type.

Products to be transported by apparatus 10 are shown in the Figs. and asillustrated are photovoltaic cells 20, which are to be joined togetherto form a string 21 which are then placed to form solar panels (notshown).

In operation photovoltaic cells 20 are placed on the beams 11, 12, and14 as shown in FIGS. 1 and 2.

Vacuum is applied to the center or movable beam 14, with vacuum off atbeams 11 and 12. The center beam 14 is raised as shown in FIGS. 3 and 4and then moved forwardly as shown in FIGS. 5 and 6, with vacuummaintained on center beam 14. The beam 14 is moved downwardly to theneutral position as shown in FIGS. 7 and 8, with vacuum turned off tocenter beam 14, and vacuum applied to the stationary beams 11 and 12,which is controlled by a sensor (not shown) of well known type. Thecenter beam 14 is dropped downwardly as shown in FIGS. 9 and 10, andretracted to the left as shown in FIGS. 11 and 12, until it reaches theposition shown in FIGS. 13 and 14, when it is raised into contact withthe cell 20, with vacuum applied to beams 11, 12, and 14. As shown inFIG. 16, an additional cell 20′ is placed next to the cell 20 as shown,vacuum is applied to the stationary beams and turned off to the centerbeam 14 when it is coplanar with side beams 11 and 12, with cell 20′soldered to the cell 20 over the stationary beams 11 and 12 in wellknown manner, while the center beam 14 is retracting.

The operation continues as described with additional cells 20′, etc.placed on beams 11, 12, and 14 and soldered together to form the string21 as shown in FIG. 15.

It should be noted that as the length of the beams 11, 12 and 14increase the number of vacuum holes 15 in the beams 11, 12 and 14 alsoincrease. As the number of holes 15 increase the effective vacuumleakage area also increases. By measuring the vacuum pressure across thelength of the beams 11, 12 and 14 with no cells 20 in place, it wasobserved that the effective vacuum decreases as you move down the beamsto the point where the cells would not be adequately clamped at the farend of the beams. If you block the holes 15, the vacuum pressureincreases. Because the cells are added to the string 21 as the string 21is “walked” down the beams, the cells act like plugs and allow thevacuum pressure to remain at acceptable levels, regardless of the beamlength. By introducing the cells 20 to the beams 11, 12 and 14 at thesame end as the vacuum source, the vacuum pressure loss is offset byprogressively blocking the holes 15 with the cells 20 and 20′. Thisallows the vacuum generator to be smaller and more energy efficient thanwould otherwise be required and also eliminates the need to createvacuum zones in the beam. While photovoltaic cells are illustrated, anywafer like product can be similarly processed.

It will thus be seen that a vacuum assisted walking beam apparatus hasbeen provided with which the objects of the invention are achieved.

We claim:
 1. A vacuum assisted walking beam apparatus for transportingand processing products placed thereon, which comprises a pair ofelongated spaced stationary side beams, a movable center beam betweensaid side beams, means for moving said center beam with respect to saidside beams in horizontal and vertical directions to transport saidproducts, said beams have a plurality of openings therein, vacuum meansin communication with said openings to selectively apply vacuum to saidopenings in said beams to hold said products during transport and whilestationary.
 2. A walking beam apparatus as defined in claim 1, in whichsaid beams are formed of metal.
 3. A walking beam apparatus as definedin claim 1, in which said products are photovoltaic cells.
 4. A walkingbeam apparatus as defined in claim 3, in which said photovoltaic cellsare placed adjacent to each other on said beams and soldered together toform strings.
 5. A walking beam apparatus as defined in claim 1, inwhich said vacuum means is selectively applied to retain said productson said center beam for transporting and said side beams for stationaryholding.
 6. A walking beam apparatus as defined in claim 1 in which saidcenter beam means for moving has three vertical positions, said threevertical positions are above the stationary beams, coplanar with thestationary beams, and below the stationary beams.
 7. A walking beamapparatus as defined in claim 5 in which sensing means is provided tosense when the center beam is coplanar with the side beams and causesaid vacuum means to be switched from said center beam to said sidebeams.